The working volume of a reciprocating piston internal combustion engine is basically a cylindrically shaped space in the engine block swept by the reciprocating piston. The same basic volume is used for the four cycle functions of intake, compression, expansion and exhaust, except as reduced by valve timing. The expansion stroke is usually so reduced and often by a substantial amount because of other considerations. The gas volume ratio of expansion to compression of these engines is often close to or less than unity. The available rotary engine also has a substantially unity ratio between expansion and compression gas volumes. An increase in expansion to compression volume ratio increases the fuel-air cycle efficiency of an engine, a substantial part of which can be translated into increased engine output. Also, with the higher expansion ratio there is more time for completion of the combustion process which results in cooler and otherwise less objectionable exhaust gas discharge to the atmosphere. For an engine with 16-1 compression ratio an increase of the expansion ratio from 16-1 to 35-1 will increase the fuel-air cycle efficiency from about 50 percent to above 60 percent. This is a fuel-air cycle efficiency increase of 20 percent or more.
In a reciprocating engine the considerable power used in reversing the inertia forces of reciprocating parts as they change directions is diverted from useful power output. Pistons and connecting rods of a two cycle engine reverse twice, and the more popular four cycle engine reverses four times per power impulse. In addition to the inertia forces per se, these forces introduce additional friction and vibration which divert additional power from the engine's useful output.
The compression ratio of both reciprocating and rotary piston engines is normally fixed and can only be changed by shop modification. For successful engine operation these engines are usually limited to a relatively narrow grade range of one type of fuel.
Easy cold weather starting is frequently used as the basis for the compression ratio of diesel engines and is a ratio usually higher than optimum for normal after start operating conditions.
Reciprocating engines have piston blow-by and crankcase pumping problems which require added controls to reduce contaminants released to the environment.
Heretofore, rotary piston engines by necessity have used a single line seal for the piston tip. This seal has been beset by wear and leakage problems. Also this engine is uneconomical in fuel consumption.
Many of the above disadvantages in reciprocating piston internal combustion engines also apply to reciprocating piston compressors, vacuum and pressure pumps and externally powered engines or motors.
My rotary piston machine overcomes the above outlined disadvantages.